Here Oliver Cowdery’s correction in 𝓟 of destroyed (spelled as destroid ) to slain was virtually immediate (the level of ink flow for the supralinear slain is unchanged). The Book of Mormon text frequently refers to slain people as being destroyed:
The verb destroy is, of course, more general than slay and can even be conjoined with slay:
However, when referring specifically to killing women and children (as in Mosiah 19:24), the text prefers the verb slain:
Note that the first of these is found in this same chapter of Mosiah 19 and refers to the same event as in verse 24. Since the correction to slain in verse 24 appears to be virtually immediate, the critical text will accept it as the reading of the original manuscript.
Summary: Maintain in Mosiah 19:24 the corrected reading in 𝓟: “their wives and their children were not slain”.